A glass containing shape-anisotropic metal fine particles, for example, silver particles or copper particles, oriented and dispersed therein is known to serve as a polarizer because the light absorption wavelength band of the metal varies depending on the direction of incident polarized light. The term “shape anisotropy” represents that longitudinal dimension and lateral dimension are different. The term “oriented” represents that the longitudinal directions of many shape-anisotropic particles are oriented in a specified direction. The term “dispersed” represents that shape-anisotropic particles are arranged with spaces.
The above-described polarizing glass is produced by, for example, performing ion exchange treatment of both main surfaces of a glass substrate to introduce Ag ions into the glass from both main surfaces thereof, forming Ag colloidal fine particles by heat treatment, and then stretching the glass substrate to provide the Ag fine particle with shape anisotropy, thereby producing a polarizing glass (refer to Non-Patent Document 1). The polarizing glass can be relatively easily produced and can be decreased in production cost, and thus the polarizing glass is attracting attention.    [Non-Patent Document 1] K. J. Berg Glass Sci. Technol. 68 C1 (1995), p554